Microsoft malware removal tool takes out Public Enemy No. 4

Microsoft this week used its Malicious Software Removal Tool to take out the fourth-biggest threat in automated program's history, which dates back to at least 2005.

The malware, known as Win32/Renocide, is a crafty backdoor-enabled worm that spreads through removable drives, network shares and popular file-sharing applications. Once installed, it drops copies of itself on all removable drives, possibly by randomizing the the file names. It also spreads by scanning machines on an infected computer's local network and pasting a copy of a file called autorun.inf, which many versions of Windows automatically execute when the drive is attached.

Renocide also plants copies of itself in shared folders of file-sharing applications and cleverly disguises them as titles of popular games and apps currently be shared on popular torrent sites.

Given its multiple propagation methods, it's not surprising that Renocide ranked as the fourth-most detected threat by the MSRT, as measured by both the number of unique machines infected and the number of detected files. The program began circulating in 2008, also contributing to its success. A member of the Microsoft Malicious Protection Center blogged about the results Wednesday here.

Once installed, Renocide may cause infected machines to connect to remote servers over Internet Relay Chat, so it can receive commands from the attackers and download other malicious programs. It also attempts to monitor the IP address of the infected machine using whatismyip.com.

Renocide is behind only malware known as Rimecud and Taterf and Sality, which are rated as Nos. 1, 2 , and 3 in terms of infected machines detected in the first week they were detected by the MSRT. More details about the backdoor worm are here and here. ®